This invention relates to blends of amorphous polyamide with a minor amount of vinyl alcohol polymer, having oxygen barrier properties which are relatively independent of humidity, and packaging films, laminates, and containers prepared therefrom.
Blends of ethylene vinyl alcohol ("EVOH") polymers with polyamides in general are known, and have been used in packaging applications as barriers to inhibit the passage of atmospheric oxygen or other gases.
Japanese patent application 53-49050 discloses a blend of ethylene vinyl alcohol copolymer (EVOH) with 5 to 40 weight percent polyamide. The EVOH contains 20-50 mole percent copolymerized ethylene, and is saponified at least 90%. The polyamides disclosed include a copolymer of hexamethylene diamine with isophthalic and terephthalic acids, in mole ratios of 100/0 to 50/50. The blend is formed into a film, which possesses gas barrier properties The barrier performance of the film is purported not to decline even in highly humid atmospheres.
U.S. Pat. No. 3,726,034, Bottenbruch et al., discloses mixtures of 70-99% polyamide and up to 30% of a hydroxyl containing polyolefin. The polyamides "consist of linear unbranched polymer chains containing no additional functional groups." Exemplified are blends of nylon 6 and EVOH.
U.S. Pat. No. 4,079,850, Suzuki et al., discloses a multi-layer blow molded container, which contains a layer which may be EVOH, polyamide, or various blends, providing gas barrier properties. The polyamides which are mentioned are nylon 6, nylon 66, and nylon 12.
U.S. Pat. No. 4,427,825, Degrassi et al., discloses a composition of matter useful for making films, of polyamide and 1-65% EVOH. Nylons with melting points greater than 175.degree. C. are preferred, such as nylon II or nylon 12.
U.S. Pat. No. 4,500,677, Maruhashi et al., discloses a resin composition comprising a mixture of two EVOH resins and a polyamide resin. The ratio of the EVOH resins to the nylon resin can be between 95:5 and 5:95. Nylon 6, nylon 6,6 and other polyamides having "linear alkylene group[s]" are specifically mentioned.